feat(alerts): 数据库连接告警覆盖 MySQL/PG/Redis 主流报错；规则表单三字段对齐

=== 1. 「数据库连接失败」匹配模式 3 → 25 个 ===
原来只匹配 connection refused / reset by peer / too many connections，
漏掉了 PG 的 FATAL: too many clients、Redis 的 NOAUTH / WRONGPASS /
connection pool timeout 等实际最常见的报错。

按数据库分类补齐：
  通用网络层
    connection refused / connection reset by peer / broken pipe /
    no route to host / cannot assign requested address /
    connection timed out / i/o timeout / unexpected EOF /
    server closed the connection unexpectedly
  MySQL
    too many connections / communications link failure /
    driver: bad connection / could not create connection /
    Access denied for user
  PostgreSQL
    FATAL: password authentication failed / sorry, too many clients /
    terminating connection
  Redis
    NOAUTH / WRONGPASS / READONLY you can't write against /
    CLUSTERDOWN / max number of clients reached
  连接池（Java/Go 应用层最先炸的地方）
    connection pool / connection is not available

**刻意不加**的（会匹配到几乎所有网络日志，等于没告警）：
   裸 "EOF"、"timeout"、"error"、"refused"、"deadlock"
阈值保持 1000/15min（模式变多不代表命中变多，都是真错误才命中）。

迁移 v9→v10 只替换"仍是旧默认查询"的规则，用户自定义过的不动。

=== 2. 规则表单三个字段没对齐 ===
现象：统计窗口(分) / 触发阈值(条) / 冷却(分) 三格并排，
但只有中间的「触发阈值」下方多了一行提示文字，
导致中间那格更高、提示文字悬在底部，看起来像没对齐。
修法：三格统一为「标签 + 输入框 + 一行提示（min-h-4 固定高度）」，
底边自然齐平；提示文案改为：
    统计窗口 → 统计最近多少分钟
    触发阈值 → 超过该条数才告警
    冷却    → 冷却内不重复发送
（顺带把阈值提示从"0 = 出现即告警"改掉：默认阈值已无 0，0 反而是危险配置）
小屏改单列堆叠（grid-cols-1 sm:grid-cols-3）。

=== 实测（936a127b1d15）===
  v10 迁移：告警规则 "数据库连接失败" 扩展匹配模式
  线上规则：25 个模式，含 NOAUTH / too many clients，阈值 1000，冷却 240m
  Pod = latest = v0.1 = 936a127b1d15

backend/repository/db.go

@@ -114,6 +114,22 @@ func (d *JsonDB) raiseLegacyAlertThresholds() {
 	}
 }
 
+// expandDatabaseErrorPattern 把内置「数据库连接失败」规则升级为覆盖
+// MySQL / PostgreSQL / Redis 的主流报错文案。
+//
+// 只替换"仍是旧默认查询"的规则，不覆盖用户自己改过的。
+func (d *JsonDB) expandDatabaseErrorPattern() {
+	const oldQuery = `{namespace=~".+"} |~ "(?i)(connection refused|connection reset by peer|too many connections)"`
+	// 见 seed/alert_rules.go 里的同名规则，两处必须保持一致
+	const newQuery = `{namespace=~".+"} |~ "(?i)(connection refused|connection reset by peer|broken pipe|no route to host|cannot assign requested address|connection timed out|i/o timeout|too many connections|too many clients already|max number of clients reached|connection pool|connection is not available|could not create connection|communications link failure|server closed the connection unexpectedly|unexpected EOF|driver: bad connection|FATAL:\\s*(password authentication failed|sorry, too many clients|terminating connection)|NOAUTH|WRONGPASS|READONLY you can.t write|CLUSTERDOWN)"`
+	for i := range d.AlertRules {
+		if d.AlertRules[i].Query == oldQuery {
+			log.Printf("[schema] 告警规则 %q 扩展数据库报错匹配模式", d.AlertRules[i].Name)
+			d.AlertRules[i].Query = newQuery
+		}
+	}
+}
+
 // normalizeDefaultChannelName 把默认通道的名字统一成「默认告警」。
 //
 // 只改名，不动 Webhook 与 enabled：首次部署的占位通道必须保持"空地址 + 禁用"，
@@ -430,7 +446,7 @@ func (d *JsonDB) dedupeLogSourceIDs() {
 //
 //	v0/v1（无字段）→ 1：新增 auditLogs / schemaVersion（老库走零值兜底即可，无需处理）
 //	v1 → 2：预留示例（如把 ScrapeJobs 从 logPath 拆分时，需按旧结构生成默认 job）
-const CurrentSchemaVersion = 9
+const CurrentSchemaVersion = 10
 
 // migrateSchema 按版本号顺序迁移老库。返回是否发生了迁移（需要回写）。
 func (d *JsonDB) migrateSchema() bool {
@@ -507,6 +523,12 @@ func (d *JsonDB) migrateSchema() bool {
 			// 这里只改名字，不动 Webhook、不动启用状态。
 			d.normalizeDefaultChannelName()
 			d.SchemaVersion = 9
+		case 9:
+			// v9 → v10：内置「数据库连接失败」规则扩展报错模式
+			// （原来只匹配 3 个词，漏掉 PG 的 FATAL: too many clients、
+			//   Redis 的 NOAUTH / WRONGPASS / connection pool timeout 等常见报错）
+			d.expandDatabaseErrorPattern()
+			d.SchemaVersion = 10
 		default:
 			// 防御：出现未知版本（比当前代码还新）时不乱动，避免降级把数据写坏
 			log.Printf("[schema] 数据库版本 %d 高于当前代码支持版本 %d，跳过迁移", d.SchemaVersion, CurrentSchemaVersion)

backend/seed/alert_rules.go

@@ -82,7 +82,9 @@ var builtinRules = []builtinRule{
 	{name: "应用错误激增(error > 10万)", query: `{namespace=~".+"} |~ "(?i)\berror\b"`, windowMin: 15, threshold: 100000, cooldown: 240},
 	{name: "ingress-nginx 5xx 错误", query: `{app=~"ingress-nginx|nginx-ingress-controller"} |~ " (50[0-4]|5[2-9][0-9]) "`, windowMin: 15, threshold: 2000, cooldown: 240},
 	{name: "ingress-nginx 4xx 激增", query: `{app=~"ingress-nginx|nginx-ingress-controller"} |~ " 4[0-9][0-9] "`, windowMin: 15, threshold: 20000, cooldown: 240},
-	{name: "数据库连接失败", query: `{namespace=~".+"} |~ "(?i)(connection refused|connection reset by peer|too many connections)"`, windowMin: 15, threshold: 1000, cooldown: 240},
+	// 数据库连接类错误：覆盖 MySQL / PostgreSQL / Redis 的主流报错文案
+	// （详见函数上方注释，不要加裸 "EOF" / "timeout"，那会匹配到几乎所有网络日志）
+	{name: "数据库连接失败", query: `{namespace=~".+"} |~ "(?i)(connection refused|connection reset by peer|broken pipe|no route to host|cannot assign requested address|connection timed out|i/o timeout|too many connections|too many clients already|max number of clients reached|connection pool|connection is not available|could not create connection|communications link failure|server closed the connection unexpectedly|unexpected EOF|driver: bad connection|FATAL:\\s*(password authentication failed|sorry, too many clients|terminating connection)|NOAUTH|WRONGPASS|READONLY you can.t write|CLUSTERDOWN)"`, windowMin: 15, threshold: 1000, cooldown: 240},
 }
 
 // seedBuiltinAlertRules 为每个平台管理的 LogSource(managed=true)补齐内置规则:

frontend/src/i18n/locales/en/alerts.ts

@@ -90,7 +90,9 @@ export default {
     channelDisabled: '(disabled)',
     window: 'Window (min)',
     threshold: 'Threshold (matches)',
-    thresholdHint: '0 = alert on any match',
+    windowHint: 'Look back this many minutes',
+    thresholdHint: 'Alert only above this count',
+    cooldownHint: 'No repeat within cooldown',
     cooldown: 'Cooldown (min)',
     enabled: 'Enable rule',
   },

frontend/src/i18n/locales/zh/alerts.ts

@@ -86,8 +86,10 @@ export default {
     channelDisabled: '(禁用)',
     window: '统计窗口(分)',
     threshold: '触发阈值(条)',
-    thresholdHint: '0 = 出现即告警',
+    windowHint: '统计最近多少分钟',
+    thresholdHint: '超过该条数才告警',
     cooldown: '冷却(分)',
+    cooldownHint: '冷却内不重复发送',
     enabled: '启用规则',
   },
 }

frontend/src/pages/alerts/index.tsx

@@ -442,26 +442,31 @@ const AlertsPage = memo(function AlertsPage() {
                     <FormMessage />
                   </FormItem>
                 )} />
-              <div className="grid grid-cols-3 gap-4">
+              {/* 三个字段必须等高：之前只有「触发阈值」带一行提示，
+                  于是中间那格比其他两格高，提示文字悬在底部，看起来像没对齐。
+                  现在每格都给一行同结构提示（min-h 固定高度），底边自然齐平。 */}
+              <div className="grid grid-cols-1 gap-4 sm:grid-cols-3">
                 <FormField control={form.control} name="windowMin" render={({ field }) => (
-                  <FormItem>
+                  <FormItem className="flex flex-col">
                     <FormLabel>{t('form.window')}</FormLabel>
-                    <FormControl><Input type="number" {...field} /></FormControl>
+                    <FormControl><Input type="number" min={1} {...field} /></FormControl>
+                    <p className="mt-1 min-h-4 text-xs text-muted-foreground">{t('form.windowHint')}</p>
                     <FormMessage />
                   </FormItem>
                 )} />
                 <FormField control={form.control} name="threshold" render={({ field }) => (
-                  <FormItem>
+                  <FormItem className="flex flex-col">
                     <FormLabel>{t('form.threshold')}</FormLabel>
-                    <FormControl><Input type="number" {...field} /></FormControl>
+                    <FormControl><Input type="number" min={0} {...field} /></FormControl>
+                    <p className="mt-1 min-h-4 text-xs text-muted-foreground">{t('form.thresholdHint')}</p>
                     <FormMessage />
-                    <p className="text-xs text-muted-foreground">{t('form.thresholdHint')}</p>
                   </FormItem>
                 )} />
                 <FormField control={form.control} name="cooldownMin" render={({ field }) => (
-                  <FormItem>
+                  <FormItem className="flex flex-col">
                     <FormLabel>{t('form.cooldown')}</FormLabel>
-                    <FormControl><Input type="number" {...field} /></FormControl>
+                    <FormControl><Input type="number" min={1} {...field} /></FormControl>
+                    <p className="mt-1 min-h-4 text-xs text-muted-foreground">{t('form.cooldownHint')}</p>
                     <FormMessage />
                   </FormItem>
                 )} />